A sharpening apparatus for forage harvester knives is disclosed in McClure et al, U.S. Pat. No. 4,834,303. McClure discloses a forage harvester with a rotating cutterhead and an automatic grinding mechanism for the knives of the cutterhead, where the grinding mechanism comprises a carriage carrying a grinding stone and is reciprocated back and forth across the cutterhead while the cutterhead is rotating. A shearbar is used in conjunction with the cutterhead.
Weaver, Jr. et al, U.S. Pat. No. 4,799,625, discloses a method and apparatus for adjusting a shearbar relative to a cutterhead. It has been found that the sharpening apparatus of McClure produces a barrel-shaped cutterhead profile over a period of time, which profile has been found incompatible with the shearbar adjusting apparatus of Weaver, Jr. et al. The apparatus of Weaver depends on contacting the two opposite corners of the rotating cutterhead to make the proper adjustment on the shearbar relative to the cutterhead profile. With a barrel-shaped cutterhead profile, it has been found that the apparatus of Weaver is contacting one corner and an intermediate portion of the cutterhead, instead of the opposite corner. The effect is that the shearbar, instead of being adjusted parallel and close to the cutterhead, is adjusted at an angle to the cutterhead, producing a gap along a substantial portion of the shearbar relative to the cutterhead. This gap is undesirable, since it causes the crop being harvested to be torn and shredded, requiring greater power and reducing the efficiency of the machinery.
The present invention is therefore directed to providing a solution to the above-identified problem.